The most important and perspective application of opposite piston mechanisms converting the reciprocal linear piston motion into rotation towards output shafts and vice versa is in the field of internal combustion engines.
There are known from DE 3347859, RU 2069273, RU 2073092, RU 2089733, RU 2118472 etc., opposite piston cam engines comprising a housing, a drive or driven shaft, a cylindrical tubular 3D cam having a cam groove on the inner cylindrical surface, opposite coaxial cylinders mounted in the housing, as well as pistons moving in the cylinders and followers having end pieces for moving in the cam groove connected to the pistons. The opposite pistons of these known cam engines are fixed each other and have synchronized motion. Although these engines have a simplified construction and possibility for reduction of contact pressure that occurs in contact areas of the cam groove and end pieces of the followers, they have not elements moving in reciprocal of the pistons direction to create balance inertial force.
There are also known from SU 1525284 and SU 1705600 another opposite piston cam engines including a housing, a drive or driven shaft, a cylindrical tubular 3D cam having a cam groove on the inner cylindrical surface, opposite coaxial cylinders mounted in the housing, as well as pistons moving in the cylinders connected with followers having end pieces for moving in the cam groove. Each piston of these engines has own follower having arm with end piece for independent movement in the cam groove. Thus it is possible for the pistons to move in opposite directions and their inertial forces to be neutralized. The end pieces for movement in the cam groove are rollers bearing by the free ends of the arms. The rectilinear movement of the pistons is ensured by other rollers mounted also on the free ends of the arms of the follower, but moving in a guide groove formed in the housing. It is a main disadvantage of these engines that the linear guidance of the followers is performed by guide groove which provokes arising of micro strokes in between the contact surfaces of the rollers and the groove when the direction of piston motion has changed. Besides in order to ensure precise guidance of the pistons, the cylinders and the pistons must be manufactured with a high precision. 3D cam is monolithic and it is difficult to produce the internal cam groove with high precision. All above complicates the technology and increases the manufacturing costs.